The present invention relates to an apparatus for controlling clutches, and more particularly to a clutch control apparatus which is capable of automatically and smoothly controlling the engaging operation of friction type clutches.
A clutch control apparatus for automatically controlling the engaging/disengaging operation of a friction type clutch has been employed in, for example, electronically controlled automatic transmission systems for vehicles. There are known prior art clutch control apparatuses of the type described above which are adapted to engage a friction type clutch at a speed corresponding to the engine speed in order to engage the clutch smoothly. However, in the conventional arrangement the time required for operating the clutch during a gear-shifting operation becomes longer if the clutch engagement speed is selected so as to reduce the shock of the clutch engagement at vehicle starting. Disadvantageously, therefore, more time is often required for gear-shift operations.
For eliminating this disadvantage, Japanese Patent Public Disclosure No. 60-11766(11766/85) discloses a clutch control system in which it is discriminated whether the clutch is being operated for a vehicle starting operation or for a gear-shift operation and the clutch engagement speed is controlled in accordance with the degree of depression of the accelerator pedal in the case where the clutch is operated for gear-shift operation. Since the disclosed apparatus is arranged so as to change the clutch engagement speed in accordance with the amount of operation of the accelerator pedal, the time required for engaging the clutch can be changed in response to the amount of operation of the accelerator pedal.
However, in the case where the clutch engagement speed is controlled as stated above, it is necessary to calculate the speed data for each clutch stroke position when fine clutch stroke control is required in the semi-engaged zone, so that the data processing becomes complex. In particular, in the case where the clutch engagement speed is relatively high, it is impractical to stop the operation of the clutch to obtain the desired clutch stroke state accurately since the data desired for the control may be scattered because of the time delay in the detection of the clutch stroke.
Furthermore, when the clutch engagement speed is controlled in accordance with the amount of operation of the accelerator pedal, there is another disadvantage that it is difficult to eliminate the dead time during which significant torque transmission is not realized through the clutch after the start of the operation for engaging the clutch. The off condition of the torque transmission due to the dead time will cause incompatibility between the vehicle acceleration expected by the driver and the actual operation of the accelerator pedal by the driver, especially when the accelerator pedal is quickly depressed.